Science fiction is a genre of fiction dealing with the impact of imagined innovations in science or technology, often in a futuristic setting.[1][2][3] It differs from fantasy in that, within the context of the story, its imaginary elements are largely possible within scientifically established or scientifically postulated laws of nature (though some elements in a story might still be pure imaginative speculation). Exploring the consequences of such differences is the traditional purpose of science fiction, making it a "literature of ideas".[4] Science fiction is largely based on writing rationally about alternative possibilities.[5] The settings for science fiction are often contrary to known reality, but the majority of science fiction relies on a considerable degree of suspension of disbelief provided by potential scientific explanations to various fictional elements.

These may include:

* A setting in the future, in alternative timelines, or in an historical past that contradicts known facts of history or the archaeological record * A setting in outer space, on other worlds, or involving aliens[6] * Stories that involve technology or scientific principles that contradict known laws of nature[7] * Stories that involve discovery or application of new scientific principles, such as time travel or psionics, or new technology, such as nanotechnology, faster-than-light travel or robots, or of new and different political or social systems (e.g., a dystopia, or a situation where organized society has collapsed)